TR4/4A Stromberg 175CD (c.1825) rich above idle

[Tim Tucker]

Hi all!
My TR-4 is running richer than I think it should at RPMs above idle. The exhaust gas analyzer you see in the pictures has been used to successfully check and adjust several cars. It's operation has also been checked against higher end equipment and on modern cars. My TR-6 was checked last week (no adjustment).

I decided to check my 'well' running TR-4. OK at idle, very rich at 3k and 1800 rpm. BTW, I tried adjusting the jets to lean it out...a complete disaster... The plugs have always looked like a rich burn was present.

What else but needle profile would have this effect?

Thanks for any feedback!
Tim

 

[bobhustead]

Review of the Heath instruction and explanation sheet reveals a number of disclosed factors that can cause inaccurate readings. Don't know how many factors are not disclosed. If, as you say, the car is well running, that is all the evidence you need to cease worrying about the meter. If adjustments that have known effects on mixture do not "improve" the readings, there is nothing wrong.
Bob

 

[poolboy]

Hotter plugs,make sure the distributor has the proper advance curve, advance the ignition timing are a few things aside from the carb adjustments.

 

[Tim Tucker]

Hotter plugs,make sure the distributor has the proper advance curve, advance the ignition timing are a few things aside from the carb adjustments.

Thanks for the response Ken! The distributor was re-built(2017) by Jeff (DBA Advance Distributor). The plugs are NGK BPR5HS (+1 hotter). Joe Curto re-bushed the bodies (2017). The carb kit came from Moss or TRF. I measured 24 degrees BTDC @ 2500rpm. 2-3 degrees at 500 rpm. 100% stock engine. With help from you and others, I was able to setup the more complicated TR-6 carbs. But the TR-4's carbs have always had this problem.TR-6 mix

 

[poolboy]

Oh, I see you're tidentenn, then...I didn't recognize you by your name.
I don't know what the timing should be on a 4's engine, maybe check back with Jeff about that 2-3* IF that's BTDC.

 

[Tim Tucker]

Oh, I see you're tidentenn, then...I didn't recognize you by your name.
I don't know what the timing should be on a 4's engine, maybe check back with Jeff about that 2-3* IF that's BTDC.

Thanks Ken...I do know if I advance the dial any more she'll 'ping'...btw, I run 93 'pure' gas...

 

[poolboy]

Float level or buoyancy, grose jets or needle valves, "choke" engagement ? ...

 

[Tim Tucker]

float level was set to .73" from carb mounting flange to highest part of float when inverted. Floats were replaced (TRF), needle valves, all carb parts replaced after the re-bush of 2017. The choke bar is flat and there's space between screw head and choke 'cam'

 

[poolboy]

OK...now I'm out of ideas, Tim

 

[Tim Tucker]

Roger that Ken. Thank you.

 

[Tim Tucker]

Reviewed my paperwork last night and found out I installed 2H after the re-bush of the carb body. Given that I have a stock TR-4 exhaust, I don't think I can take advantage of the increased gas flow. Need that exhaust header. For the short term, putting 2A needles back in.

 

[Tim Tucker]

I fitted the Rimmer Brothers exhaust kit RF4076 and got what one would expect: a huge leaning of my mix. What a difference over a stock 4 manifold. Should have changed that years ago. Still a tad rich at idle.

 

[sp53]

interesting